Swaging machine for the internal profiling of tubular workpieces

ABSTRACT

Mandrel means formed with a shoulder are adapted to enter said workpiece so that the latter surrounds said shoulder. A plurality of dies are spaced around said mandrel means and adapted to swage said workpiece onto said mandrel means. A gripping head surrounds said mandrel means and is adapted to axially support said workpiece at one end thereof and operable to rotate said workpiece about its axis and to advance it toward said dies at the same time. A holder-up is adapted to axially support said workpiece at the opposite end thereof and movable in the axial direction of said workpiece. Means are provided to apply a hydraulic backpressure to said holder-up so that the same yieldably resists the movement of said workpiece as the same is advanced by said gripping head. The gripping head comprises means defining a chamber adapted to contain a cushion of liquid under pressure, which cushion is adapted to axially support said workpiece, and a piston interposed between said cushion and said workpiece and surrounding said mandrel means. The machine also comprises valve means operable to reduce the pressure of said cushion when said shoulder enters between said dies.

United States Patent 1191 Kralowetz Aug. 21, 1973 SWAGING MACHINE FORTHE INTERNAL PROFILING OF TUBULAR WORKPIECES [76] Inventor: BrunoKralowetz, Weinleiten 142,

St. Ulrich near Steyr, Austria [22] Filed: Apr. 21, 1972 [21] Appl. No.:246,137

[30] Foreign Application Priority Data Primary Examiner-Lowell A. LarsonAttorney-Kurt Kelman r H 7 s 24 25 u 57 Y ABSTRACT Mandrel means formedwith a shoulder are adapted to enter said workpiece so that the lattersurrounds said shoulder. A plurality of dies are spaced around saidmandrel means and adapted to swage said workpiece onto said mandrelmeans. A gripping head surrounds said mandrel means and is adapted toaxially support said workpiece at one end thereof and operable to rotatesaid workpiece about its axis and to advance it toward said dies at thesame time. A holder-up is adapted to axially support said workpiece atthe opposite end thereof and movable in the axial direction of saidworkpiece. Means are provided to apply a hydraulic backpressure to saidholder-up so that the same yieldably resists the movement of saidworkpiece as the same is advanced by said gripping head. The grippinghead comprises means defining a chamber adapted to contain a cushion ofliquid under pressure, which cushion is adapted to axially support saidworkpiece, and a piston interposed between said cushion and saidworkpiece and surrounding said mandrel means. The machine also comprisesvalve means operable to reduce the pressure of said cushion when saidshoulder enters between said dies.

8 Claims, 4 Drawing Figures SWAGING MACHINE FOR THE INTERNAL PROFILING FTUBULAR WORKPIECES This invention relates to a swaging machine for theinside profiling of tubular workpieces, particularly of barrels offirearms, by die impacts over an offset mandrel, in which machine theworkpiece is gripped be tween a gripping head, which feeds the workpieceto the dies and rotates it at the same time, and a holderup, which issubjected to a constant backpressure by a liquid and against saidbackpressure is 'forced back as the workpiece advances, and the mandrelis secured to a rod, which extends through the gripping head.

Because the workpiece is gripped between the gripping head at one endand the holderup at the other end, the swaging results in a moreaccurate inside "profile as the length of the workpieces cannot 'bechanged by the die blows so that the depth action of each blow isincreased. it has now "been found that the use of a constant grippingforce cannot lead to satisfactory results if an internal shoulder isformed in one-operation, e.g., a chamber is formed next to the groovedbarrel. When the workpiece has been swaged onto the shoulder-formingportion of the mandrel so that a sharp edged shoulder has been formed,said shoulder will be stretched as the advance of the workpiece underthe dies is continued and the axial flow of material forces thepreviously swaged internal edge away from the associated shoulder of themandrel. During the next die blow, the mandrel shoulder is then forcedinto the workpiece once more so that inaccurate steps similar to aflight of stairs are formed.

To avoid this disadvantage, a swaging machine has been developed inwhich the workpiece is also firmly axially supported by the grippinghead but the hydraulic backpressure applied to the holder-up independence on the desired internal shape of the workpiece portiondisposed between the dies at any time can be automatically varied bymeans of at least one valve or the like, which is incorporated in thereturn conduit for the displaced liquid under pressure. As a result, thepresstressing force applied to that portion of the work piece which isadjacent to the holder-up is not constant but increases when an internalshoulder or the like is being swaged so that the workpiece cannot bestretched toward the holder-up and material cannot flow from thepreviously swaged shoulder formed under the action of the mandrel at thebeginning of the chamber. Practice has shown, however, that the forceswhich arise are often too large or the holder-up cannot apply the largebackpressure forces required to prevent a stretching of the workpiece sothat a satisfactory forging cannot be produced.

It is thus an object of the invention to eliminate this disadvantage andso to improve a forging machine as defined first hereinbefore that asatisfactory inside profiling of workpieces having internal shoulders isensured.

In accordance with the invention, this object is essentiallyaccomplished in that the workpiece is axially supported in the grippinghead by a cushion of liquid under pressure through the intermediary of apiston, through which the mandrel extends, and the pressure applied tosaid cushion is adapted to be reduced by a valve or the like, which ispreferably adapted to be additionally connected to the circuit, when thestep of the mandrel enters the swagingzone between the dies. Hence, whenit is desired to forge a shoulder the backpressure isnot increased butthe pressure of the cushion of liquid under pressure is reduced so thatthe material of the workpiece adjacent to the grippinghead can flowtoward the gripping head. This has the important advantage that evenwhen the advance of the workpiece is continued does the material of theworkpiece hug the step-forming shoulder of the mandrel and is not forcedaway from said shoulder in the feeding direction. Once the shoulder hasbeen swaged, it is preserved as the swaging is continued, and aformation of inaccurate steps similar to a flight of stairs need not befeared. Excessively strong forces are also avoided because during theswaging of a shoulder the axial prestressing force need not be increasedbut is even reduced adjacent to the gripping head.

It will be particularly desirable if the cylinder chamber which containsthe cushion of liquid under pressure is fed by a pump through a conduitwhich is provided with a check valve and a pressure-regulating valve,Le, a valve which acts to maintain a constant pressure, and a secondpressure-regulating valve which is responsive to a much lower pressureis adapted to be connected to the circuit by means of a solenoid valve,which is operable by a limit switch or the like. While the barrel isbeing swaged, the pressure of the cushion of liquid under pressure iscontrolled by the first pressureregulating valve. When the shoulder onthe mandrel enters the swaging zone between the hammers, a suitablyoffset stop, cam or the like acts on the limit switch, which thenoperates the solenoid valve to connect the second pressure-regulatingvalve to the circuit so that the latter valve now controls the pressureof the cushion of liquid under pressure. This pressure of the cushion isthus reduced and the piston which axially supports the workpiece can bepushed back opposite to the feeding direction under the action of theflow of the material. A comparatively simple hydraulic device is thusprovided, which enables an automatic connection of the second valve intothe circuit, provided that the stop, cam or the like for the limitswitch is positioned as may be required.

To provide this simple design, the piston for axially supporting theworkpiece is non-rotatably and axially slidably mounted in a sleeve,which defines the cylinder chamber for the cushion of liquid underpressure and which is rotatably and axially undisplaceably mounted inthe gripping head.

An embodiment of the invention is shown by way of example on theaccompanying drawings, in which FIG. 1 is a diagrammatic view, partly insection, showing an entire machine, and

FIGS. 2 to 4 are similar views showing the essential parts of themachine in three different operating position's.

Swaging dies 1 together with means, not shown, for driving them andmeans for varying the stroke position of the dies are mounted in aswaging box 2, which is preceded by a bed 3 for a displaceable grippinghead 4. Rods 5 extend through the swaging box 2 and engage the grippinghead 4. The rods 5 are connected to pistons 6, which are slidable incylinders 7 secured to the swaging box 2. Through conduits 8, liquidunder pressure delivered by a pump 9 is supplied to the pistons 6 sothat the gripping head 4 is advanced toward the dies 1. A sleeve 10 isrotatably and axially nondisplaceably mounted in the gripping head 4 andis driven by a motor 11. A piston 12 which serves to directly axiallysupport a workpiece 13 is nonrotatably and axially slidably mounted inthe sleeve. A cushion 14 of liquid under pressure is contained in thatcylinder chamber which is remote from the workpiece 13. The cushion issupplied by a pump 15, which is connected by a conduit 16 to therespective cylinder chamber. The conduit 16 extends from the pump 15through a check valve 17 and is provided with a pressure-regulatingvalve 18. A solenoid valve 19 is operable by a limit switch, not shown,to connect a second pressureregulating valve 20 to the circuit. Thissecond valve is set to a much lower pressure than the pressureregulatingvalve 18.

A yoke 21 is disposed between the two cylinders 7 and has anothercylinder 22 secured to it. A rotatable holder-up 24 is axially supportedby a piston 23 mounted in the cylinder 22. Pressure is applied to oneend of the piston 23 by a pump 25. A pressureregulating valve 26controls the backpressure of the liquid, which is displaced from thecylinder 22 during the movement of the holder-up. The workpiece 13consists, e.g., of a barrel of a firearm and is axially gripped betweenthe piston 12 of the gripping head 4 and the holder-up 24. As theworkpiece is advanced by the pistons 6, the holder-up 24 and piston 23are forced back and the liquid under pressure is forced back through thevalve 26 into the oil reservoir (FIGS. 1 and 2). A rod 27 extendsthrough the gripping head and the gripping head sleeve as well as thepiston 12. A mandrel 28 is secured to the rod 27 and adapted to beretracted by an actuator 29. While the barrel and its grooves are beingswaged, a portion 28' of the mandrel 28 is disposed between the dies 1(FIG. 1). At the end of the barrel, the right-hand end of the mandrelengages an internal shoulder of the gripping head sleeve 10 so that themandrel 28 together with the gripping head 4 is carried along toward thedies against the action of the hydraulic pressure in the actuator 29(FIG. 2). When the mandrel step 28" has reached the swaging zone betweenthe dies '1, the solenoid valve 19 is operated to connect thepressure-regulating valve 20 to the circuit so that the pressure of thecushion 14 of liquid under pressure is reduced and the material of theworkpiece can flow toward the gripping head 4 and can force back thepiston 12 (FlGS. 3 and 4). When the swaging has been completed, theactuator 22, 23 for the holder-up returns the entire apparatus back toits initial position and the finished workpiece is removed.

What is claimed is:

1. A swaging machine for the internal profiling of a tubular workpiece,which comprises mandrel means formed with a shoulder and adapted toenter said workpiece so that the latter surrounds said shoulder,

a plurality of dies spaced around said mandrel means and operable toswage said workpiece onto said mandrel means,

a gripping head surrounding said mandrel means and adapted to axiallysupport said workpiece at one end thereof and operable to rotate saidworkpiece about its axis and to advance it toward said dies at the sametime,

a holder-up adapted to axially support said workpiece at the-oppositeend thereof and movable in the axial direction of said workpiece, andmeans for applying a hydraulic backpressure to said holder-up so thatthe same yieldably resists the movement of said workpiece as the same isadvanced by said gripping head,

said gripping head comprising means defining a chamber adapted tocontain a cushion of liquid under pressure, which cushion is adapted toaxially support said workpiece, and a piston interposed between saidcushion and said workpiece and surrounding said mandrel;

said machine also comprising valve means operable to reduce the pressureof said cushion when said shoulder enters between said dies.

2. A swaging machine as set forth in claim 1, in which said grippinghead is adapted to axially support said mandrel means adjacent to saidone end of said workpiece and operable to advance said mandrel meanstoward said dies.

3. A swaging machine as set forth in claim 1, which is operable to forman internal profile in a tubular workpiece so as to produce a firearmbarrel.

4. A swaging machine as set forth in claim 1, in which said mandrelmeans extend through said gripping head and comprise a mandrel formedwith said shoulder and protruding from said gripping head toward saidholderup and a mandrel rod connected to said mandrel at the end thereofremote from said holder-up.

5. A swaging machine as set forth in claim 1, which comprises ahydraulic circuit for controlling the pressure of said cushion,

said valve means being adapted to be connected to said hydrauliccircuit.

6. A swaging machine as set forth in claim 5, in which said hydrauliccircuit comprises a pump, a conduit connecting said pump to saidcushion, a check valve incorporated in said cushion, and a firstpressure-regulating valve connected to said conduit between said checkvalve and said cushion, and said valve means comprise a secondpressure-regulating valve set to a much lower pressure than said firstregulating valve and a connecting valve operable to connect said secondregulating valve to said conduit between said check valve and saidcushion.

7. A swaging machine as set forth in claim 6, in which said connectingvalve consists of a solenoid valve and a limit switch is provided, whichis operable thus to operate said solenoid valve when said mandrel meanshave reached a predetermined position relative to said dies.

8. A swaging machine as set forth in claim 1, in which said grippinghead comprises a gripping head body which is movable toward said dies,

said means defining said chamber comprise a sleeve,

which is rotatably and axially nondisplaceably mounted in said grippinghead body, and

said piston is nonrotatably and axially slidably mounted in saidchamber.

k k I I.

1. A swaging machine for the internal profiling of a tubular workpiece,which comprises mandrel means formed with a shoulder and adapted toenter said workpiece so that the latter surrounds said shoulder, aplurality of dies spaced around said mandrel means and operable to swagesaid workpiece onto said mandrel means, a gripping head surrounding saidmandrel means and adapted to axially support said workpiece at one endthereof and operable to rotate said workpiece about its axis and toadvance it toward said dies at the same time, a holder-up adapted toaxially support said workpiece at the opposite end thereof and movablein the axial direction of said workpiece, and means for applying ahydraulic backpressure to said holder-up so that the same yieldablyresists the movement of said workpiece as the same is advanced by saidgripping head, said gripping head comprising means defining a chaMberadapted to contain a cushion of liquid under pressure, which cushion isadapted to axially support said workpiece, and a piston interposedbetween said cushion and said workpiece and surrounding said mandrel;said machine also comprising valve means operable to reduce the pressureof said cushion when said shoulder enters between said dies.
 2. Aswaging machine as set forth in claim 1, in which said gripping head isadapted to axially support said mandrel means adjacent to said one endof said workpiece and operable to advance said mandrel means toward saiddies.
 3. A swaging machine as set forth in claim 1, which is operable toform an internal profile in a tubular workpiece so as to produce afirearm barrel.
 4. A swaging machine as set forth in claim 1, in whichsaid mandrel means extend through said gripping head and comprise amandrel formed with said shoulder and protruding from said gripping headtoward said holder-up and a mandrel rod connected to said mandrel at theend thereof remote from said holder-up.
 5. A swaging machine as setforth in claim 1, which comprises a hydraulic circuit for controllingthe pressure of said cushion, said valve means being adapted to beconnected to said hydraulic circuit.
 6. A swaging machine as set forthin claim 5, in which said hydraulic circuit comprises a pump, a conduitconnecting said pump to said cushion, a check valve incorporated in saidcushion, and a first pressure-regulating valve connected to said conduitbetween said check valve and said cushion, and said valve means comprisea second pressure-regulating valve set to a much lower pressure thansaid first regulating valve and a connecting valve operable to connectsaid second regulating valve to said conduit between said check valveand said cushion.
 7. A swaging machine as set forth in claim 6, in whichsaid connecting valve consists of a solenoid valve and a limit switch isprovided, which is operable thus to operate said solenoid valve whensaid mandrel means have reached a predetermined position relative tosaid dies.
 8. A swaging machine as set forth in claim 1, in which saidgripping head comprises a gripping head body which is movable towardsaid dies, said means defining said chamber comprise a sleeve, which isrotatably and axially nondisplaceably mounted in said gripping headbody, and said piston is nonrotatably and axially slidably mounted insaid chamber.